Image encoding method using a skip mode, and a device using the method

ABSTRACT

Disclosed are an image encoding method using a skip mode and a device using the method. The image encoding method may comprise the steps of: judging whether there is residual block data of a prediction target block on the basis of predetermined data indicating whether residual block data has been encoded; and, if there is residual block data, restoring the prediction target block on the basis of the residual block data and an intra-screen predictive value of the prediction target block. Consequently, encoding and decoding efficiency can be increased by carrying out the encoding and decoding of screen residual data only for prediction target blocks where there is a need for a residual data block in accordance with screen similarity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. patentapplication Ser. No. 17/216,881, filed on Mar. 30, 2021, which is aContinuation Application of U.S. patent application Ser. No. 16/743,044,filed on Jan. 15, 2020, now U.S. Pat. No. 10,992,956, which is aContinuation Application of U.S. patent application Ser. No. 16/151,627,filed on Oct. 4, 2018, now U.S. Pat. No. 10,575,014, which is aContinuation Application of U.S. patent application Ser. No. 14/005,493,having a 371(c) date of Sep. 16, 2013, now U.S. Pat. No. 10,142,623,issued on Nov. 27, 2018, which is a U.S. National Stage Application ofInternational Application No. PCT/KR2012/002763, filed on Apr. 12, 2012,which claims the benefit under 35 USC 119(a) and 365(b) of Korean PatentApplication No. 10-2011-0033780, filed on Apr. 12, 2011 and KoreanPatent Application No. 10-2012-0037914, filed on Apr. 12, 2012, in theKorean Intellectual Property Office, the entire disclosures of which areincorporated herein by reference for all purposes.

TECHNICAL FIELD

The present invention relates to a decoding method and apparatus, andmore particularly, to a video decoding method using a skip mode and anapparatus using the same.

BACKGROUND ART

Recently, the demand for high resolution and high quality video such asa high definition (HD) video and an ultra high definition (UHD) videohas increased in various applications. As resolution and quality ofvideo data have increased, a data amount relatively increases ascompared to existing video data. Therefore, when the video data aretransmitted using media such as an existing wired and wireless broadbandline or are stored using the existing storage media, transmission costsand storage costs increase. In order to solve these problems occurringdue to the increase in the resolution and quality of the video data,high efficiency video compression technologies may be utilized.

As the video compression technologies, there are various technologiessuch as an inter prediction technology of predicting pixels valuesincluded in a current picture from pictures before or after the currentpicture, an intra prediction technology of predicting pixel valuesincluded in a current picture using pixel information in the currentpicture, and an entropy coding technology of allocating a short code toa value having high appearance frequency and a long code to a valuehaving low appearance frequency, and the like. The video data may beeffectively compressed, transmitted, or stored by using the videocompression technologies.

DISCLOSURE Technical Problem

The present invention provides a method of recovering a video havinghigh pixel correlation.

The present invention also provides an apparatus for performing arecovering method on a video having high pixel correlation.

Technical Solution

In an aspect, a video decoding method is provided. The video decodingmethod includes: determining whether residual block information of aprediction object block is present based on predetermined informationrepresenting whether the residual block information is encoded; andrecovering the prediction object block based on an intra predictionvalue and the residual block information when the residual blockinformation is present. The video decoding method may further include:recovering the prediction object block by using only the intraprediction value of the prediction object block when the residual blockinformation is absent. The intra prediction value may be a valuecalculated based on a reference pixel value of the prediction objectblock and may be a value predicted while having directivity according toa predetermined intra prediction mode or may be an arithmetic averagevalue or a weight average value of reference pixels. The video decodingmethod may further include: decoding reference pixel value informationselectively used upon performing the intra prediction on the predictionobject block. The intra prediction value may be an intra predictionvalue calculated based on the reference pixel value selected inconsideration of characteristics of the reference pixels of theprediction object block. The reference pixel value selected inconsideration of the characteristics of the reference pixels of theprediction object block may be a reference pixel value selected bycomparing similarity of an upper left pixel and a left reference pixelof the prediction object block with similarity of an upper left pixeland an upper reference pixel of the prediction object block. The intraprediction value may be a value calculated based on an average value ora sum of weight values of values predicted by a plurality of intraprediction mode. The predetermined information representing whether theresidual block information is encoded may be information induced fromperipheral block information of the already decoded prediction objectblock.

In another aspect, a video decoding apparatus is provided. The videodecoding apparatus includes: an entropy decoder decoding informationrepresenting whether residual block data are parsed; and a predictordetermining whether at least one of residual block information andprediction block generation information of a prediction object block ispresent, based on decoded intra skip flag information. The predictor maybe a predictor recovering the prediction object block based on an intraprediction value and the residual block information of the predictionobject block when the residual block information is present. Thepredictor may be a predictor recovering the prediction object block byusing only the intra prediction value of the prediction object blockwhen the residual block information is absent. The intra predictionvalue may be a value calculated based on a reference pixel value of theprediction object block and may be a value predicted while havingdirectivity according to a predetermined intra prediction mode or may bean arithmetic average value or a weight average value of referencepixels. The predictor may be a predictor performing the intra predictionbased on only the selectively used reference pixel value information.The intra prediction value may be an intra prediction value calculatedbased on the reference pixel value selected in consideration ofcharacteristics of the reference pixels of the prediction object block.The reference pixel value selected in consideration of thecharacteristics of the reference pixels of the prediction object blockmay be a reference pixel value selected by comparing similarity of anupper left pixel and a left reference pixel of the prediction objectblock with similarity of an upper left pixel and an upper referencepixel of the prediction object block. The intra prediction value may bea value calculated based on an average value or a sum of weight valuesof values predicted by a plurality of intra prediction mode. Theinformation representing whether the residual block data are parsed maybe information induced from peripheral block information of the alreadydecoded prediction object block.

Advantageous Effects

A video decoding method using a skip mode and the apparatus using thesame in accordance with the exemplary embodiment of the presentinvention perform the encoding and decoding on residual information of ascreen for only the prediction object block requiring the residualinformation block on the basis of the screen similarity, thereby makingit possible to increase the encoding and decoding efficiency.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a video encoding apparatus inaccordance with an exemplary embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a videodecoding apparatus in accordance with another exemplary embodiment ofthe present invention.

FIG. 3 is an image illustrating a depth information video in accordancewith an exemplary embodiment of the present invention.

FIG. 4 is a graph illustrating a direction of an image and pixelsimilarity in accordance with an exemplary embodiment of the presentinvention.

FIG. 5 is a conceptual diagram illustrating a block encoding method inaccordance with an exemplary embodiment of the present invention.

FIG. 6 is a conceptual diagram illustrating a block decoding method inaccordance with an exemplary embodiment of the present invention.

FIG. 7 is a conceptual diagram illustrating a directional intraprediction mode in accordance with an exemplary embodiment of thepresent invention.

FIG. 8 is a conceptual diagram illustrating an intra prediction methodin accordance with an exemplary embodiment of the present invention.

FIG. 9 is a conceptual diagram illustrating an intra prediction methodin accordance with an exemplary embodiment of the present invention.

FIG. 10 is a conceptual diagram illustrating an intra prediction methodin accordance with an exemplary embodiment of the present invention.

FIG. 11 is a conceptual diagram illustrating a method for determiningwhether a residual block is generated in accordance with an exemplaryembodiment of the present invention.

FIG. 12 is a flow chart illustrating a video decoding method inaccordance with an exemplary embodiment of the present invention.

FIG. 13 is a conceptual diagram illustrating a method for recoveringmulti-dimensional video in accordance with an exemplary embodiment ofthe present invention.

MODE FOR INVENTION

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.However, in describing exemplary embodiments of the present invention,well-known functions or constructions will not be described in detailsince they may unnecessarily obscure the understanding of the presentinvention.

It is to be understood that when any element is referred to as being“connected to” or “coupled to” another element, it may be connecteddirectly to or coupled directly to another element or be connected to orcoupled to another element, having the other element interveningtherebetween. Further, in the present specification, in the case ofdescribing “including” a specific component, it is to be understood thatadditional components other than a corresponding component are notexcluded, but may be included in exemplary embodiments or the technicalscope of the present invention.

Terms used in the specification, ‘first’, ‘second’, etc., may be used todescribe various components, but the components are not to be construedas being limited to the terms. That is, the terms are used todistinguish one component from another component. For example, the‘first’ component may be named the ‘second’ component, and vice versa,without departing from the scope of the present invention.

In addition, components described in exemplary embodiments of thepresent invention are independently shown only in order to indicate thatthey perform different characteristic functions. Therefore, thecomponents that are independently shown do not mean that each of thecomponents may not be implemented as one hardware or software. That is,each of the components is divided for convenience of explanation, aplurality of components may be combined with each other to thereby beoperated as one component or one component may be divided into aplurality components to thereby be operated as the plurality ofcomponents, which are included in the scope of the present invention aslong as it departs from essential characteristics of the presentinvention.

In addition, some of components may not be indispensable componentsperforming essential functions of the present invention, but beselective components improving only performance thereof. The presentinvention may also be implemented only by a structure including theindispensible components except for the selective components, and thestructure including only the indispensible components is also includedin the scope of the present invention.

FIG. 1 is a block diagram illustrating a video encoding apparatus inaccordance with an exemplary embodiment of the present invention.

Referring to FIG. 1 , an apparatus 100 for encoding video includes amotion predictor 111, a motion compensator 112, an intra predictor 120,a switch 115, a subtracter 125, a transformer 130, a quantizer 140, anentropy encoder 150, a dequantizer 160, an inverse transformer 170, anadder 175, a filter unit 180, and a reference video buffer 190.

The apparatus 100 for encoding video performs encoding on an input videoby an intra mode (intra prediction mode) or an inter mode (interprediction mode) and outputs bit streams. Hereinafter, in the exemplaryembodiment of the present invention, the intra prediction may be used asthe same meaning as intra prediction and the inter prediction may beused as the same meaning as inter prediction. In order to determine anoptimal prediction method for a prediction unit, an intra predictionmethod and an inter prediction method for a prediction unit may beselectively used. The apparatus 100 for encoding video may generate aprediction block for an original block of the input video and then,encode a difference between the original block and the prediction block.

In the case of the intra prediction mode, the intra predictor 120(alternatively, the intra-picture predictor may be used as a term havingthe same meaning) generates a prediction block by performing spatialprediction using pixel values of the already encoded block around acurrent block.

The exemplary embodiment of the present invention may determine whetherto encode a residual block that is a difference value between predictionvalues of the original block and a prediction object block, on the basisof pixel correlation of video for prediction values of the predictionobject block calculated by performing the intra prediction on theprediction object block. For example, in the case of a block having highpixel correlation like depth video, information in which the residualblock is not encoded and the prediction object block is constructed(generated) by only the prediction values may be transmitted to adecoder. Video encoding efficiency may be improved by the method. Theinformation regarding whether the residual block and prediction blockgeneration information is encoded may be represented based on any flaginformation. For example, (1) when a flag value is 0, the predictionobject block is a block in which the residual block is also encoded andtherefore, the entropy decoder decodes, dequantizes, and inverselytransforms the residual block information and then, adds the informationto the prediction value of the prediction object block generated fromthe predictor, thereby making it possible to recover the video. (2) Whena flag value is 1, the prediction object block is a block in which theresidual block is not encoded and the recovered video may be generatedby only the prediction value of the prediction object block generatedfrom the predictor.

In the case of the inter prediction mode, the motion predictor 111searches a region optimally matched with the input block in a referencevideo stored in the reference video buffer 190 during the motionprediction process to obtain a motion vector. The motion compensator 112performs motion compensation using the motion vector to generate theprediction block.

The subtracter 125 may generate the residual block by a differencebetween the input block and the generated prediction block. Thetransformer 130 may perform transform on the residual block to outputtransform coefficients. Further, the quantizer 140 quantizes the inputtransform coefficients on the basis of quantization parameters to outputquantized coefficients. The entropy encoder 150 performs entropyencoding on the input quantized coefficients according to probabilitydistribution to output bit streams.

At the time of performing the inter prediction encoding, the currentlyencoded video should be decoded and stored so as to be used as thereference video. Therefore, the quantized coefficients are dequantizedby the dequantizer 160 and inversely transformed by the inversetransformer 170. The dequantized, inversely transformed coefficients areadded to the prediction block by the adder 175 and thus, the recoveredblock is generated.

The recovered block passes through the filter unit 180, wherein thefilter unit 180 may apply at least one of a deblocking filter, a sampleadaptive offset (SAO), an adaptive loop filter (ALF) to the recoveredblock or the recovered picture. The filter unit 180 may be referred toas an adaptive in-loop filter. The deblocking filter may remove blockdistortion occurring at a boundary between blocks. The SAO may add anoptimal offset value to the pixel value so as to compensate for codingerrors. The ALF may perform filtering based on a value obtained bycomparing the recovered video with the original video and may also beperformed only when the high efficiency coding is applied. The recoveredblock passing through the filter unit 180 is stored in the referencevideo buffer 190.

FIG. 2 is a block diagram illustrating a configuration of a videodecoding apparatus in accordance with another exemplary embodiment ofthe present invention.

Referring to FIG. 2 , an apparatus 200 for decoding video includes anentropy decoder 210, a dequantizer 220, an inverse transformer 230, anintra predictor 240, a motion compensator 250, a filter unit 260, and areference video buffer 270.

The apparatus 200 for decoding video may receive the bit streams outputfrom the encoder and perform the decoding in the intra mode or the intermode to output the reconstructed video, that is, the recovered video. Inthe case of the intra mode, the prediction block is generated using theintra prediction mode and in the case of the inter mode, the predictionblock is generated using the inter prediction method. The apparatus 200for decoding video may obtain the residual block from the received bitstreams, generate the prediction block, and then add the predictionblock to the residual block to generate the reconstructed block, thatis, the recovered block.

The entropy decoder 210 performs the entropy decoding on the input bitstream according to the probability distribution to output the quantizedcoefficients. The quantized coefficients may be dequantized by thedequantizer 220 and be inversely transformed by the inverse transformer230. In this case, the quantized coefficients may bedequantized/inversely transformed to generate the residual block.

As described above, the prediction object block may be divided into ablock transmitted by encoding only the information in which theprediction object block is constructed (generated) by only theprediction value and a block transmitted by being encoded together withthe residual block information. In this case, the predetermined flag isdecoded by the entropy decoder so as to determine whether the predictionobject block is encoded together with the residual block information andit may be determined whether the residual block is decoded or theresidual block is not decoded, on the basis of a decoded intra skipflag. For example, (1) when the intra skip flag is 0, the predictionobject block is a block in which the residual block is also encoded andtherefore, the entropy decoder decodes, dequantizes, and inverselytransforms the residual block information and then, adds the informationto the prediction value of the prediction object block generated fromthe predictor, thereby making it possible to recover the video. (2) Whenthe intra skip flag is 1, the prediction object block is a block inwhich the residual block is not encoded and the recovered video may begenerated by only the prediction value of the prediction object blockgenerated from the predictor.

In the case of the intra prediction mode, the intra predictor 240(alternatively, the inter-picture predictor) generates the predictionblock by performing the spatial prediction using pixel values of thealready encoded block around the current block.

In the case of the inter prediction mode, the motion compensator 250 mayperform the motion compensation using the motion vector and thereference video stored in the reference video buffer 270 to generate theprediction block.

The residual block and the prediction block are added by the adder 255and the added block passes through the filter unit 260. The filter unit260 may be applied to at least one of the deblocking filter, the SAO,and the ALF to the recovered block or the recovered picture. The filterunit 260 outputs the reconstructed video, that is, the recovered video.The recovered video may be stored in the reference video buffer 270 tobe used for the inter prediction.

As a method for improving prediction performance of theencoding/decoding apparatus, there are a method for increasing accuracyof interpolation video and a method for predicting a difference signal.Here, the difference signal is a signal representing the differencebetween the original video and the prediction video. In thespecification, the “difference signal” may alternatively be used as the“differential signal”, the “residual block”, or the “differential block”according to the syntax, which may be differentiated by a person skilledin the art to which the present invention pertains within the range notaffecting the idea and essence of the present invention.

As described above, in the exemplary embodiment of the presentinvention, a coding unit is used as an encoding unit for convenience ofexplanation, but may also be a unit performing the encoding and thedecoding. The meaning of each component included in the video encoderand the video decoder may also include a hardware meaning as well as asoftware processing unit that may be performed through an algorithm.

In addition, the video encoding apparatus and the video decodingapparatus may be used to encode and decode video information of athree-dimensional video encoding and decoding method, for example, depthvideo information, multi-view video information. Therefore, the videoencoded and decoded in the exemplary embodiment of the present inventionmay be the depth information video including a depth information map andmay also be video including luminance information or color differenceinformation.

In the exemplary embodiment of the present invention, the video encodingmethod and the video decoding method to be described below may beperformed in each component included in the video encoder and the videodecoder that are described above in FIGS. 1 and 2 . The meaning ofcomponents may include the hardware meaning as well as the softwareprocessing unit that may be performed through an algorithm.

FIG. 3 is an image illustrating a depth information video in accordancewith an exemplary embodiment of the present invention.

Referring to FIG. 3 , the depth information map includes the informationrepresenting a distance between a camera and an object and therefore,inter-pixel correlation is very high. In particular, the same depthinformation may be widely represented in an object or a background part.

FIG. 4 is a graph illustrating a direction of an image and pixelsimilarity in accordance with the exemplary embodiment of the presentinvention.

The graph of FIG. 4 represents a 2D graph representing values of eachpixel in a horizontal direction or a vertical direction from anyposition of the video depth information video of FIG. 3 . It can beappreciated from the graph that the depth information map has very highinter-pixel correlation with peripheral blocks and the values of thedepth information in the object of the depth information map and at thebackground part are similar to one another.

When the intra prediction is performed in the video having the highinter-pixel correlation, the pixel value of the prediction object blockmay be substantially predicted using only the pixel values of theperipheral blocks and therefore, the encoding process and the decodingprocess for the residual signal that is the difference value between thecurrent block and the prediction block are not required. Therefore, theinformation in which the prediction object block is constructed(generated) by only the prediction value without transmitting theresidual block information according to the video characteristics may betransmitted to the decoder and the encoding efficiency may be increasedby the above-mentioned method.

The exemplary embodiment of the present invention discloses an encodingmethod for reducing calculation complexity and improving the encodingefficient at the time of performing the intra prediction encoding on thevideo having the high inter-pixel correlation like the depth informationvideo. The exemplary embodiment of the present invention may also beapplied to the video information including a luminance sample or a colordifference sample rather than the depth information video, which isincluded in the scope of the present invention.

Hereinafter, in the exemplary embodiment of the present invention, theblock that is an object of the intra prediction is defined as the termcalled the prediction object block, the block generated by performingthe intra prediction on the prediction object block is defined as theterm called the prediction block, the block that is the prediction blockis defined as the term called the original block, and the block thatrepresents the difference between the prediction block and the originalblock is defined as the term called the residual block.

FIG. 5 is a conceptual diagram illustrating a block encoding method inaccordance with an exemplary embodiment of the present invention.

Referring to FIG. 5 , the video may be encoded by selecting one of themethod (1) for encoding the residual block that is the difference valuebetween the prediction block and the input video generated by thepredictor (inter prediction and intra prediction) and the method (2) forencoding only the prediction block generated by the predictor (interprediction and intra prediction). Whether the encoding for the generatedresidual block is performed or whether the video is encoded using onlythe prediction block may be represented based on syntax elementinformation like the predetermined flag information. Hereinafter, thesyntax element information is defined as the term called the intra skipflag.

The above-mentioned method (1) may perform the transform, thequantization, and the entropy encoding on the residual block for theprediction object block at the time of performing the transform and thequantization on the residual block to generate the bit stream. Thetransformed and quantized block may be included in the buffer by beingsubjected to the inverse transform and the dequantization so as to beagain used for the prediction.

The above-mentioned method (2) does not encode the prediction blockgeneration information (for example, in the case of the intraprediction, the intra prediction mode information and in the case of theinter prediction, the motion vector, the reference picture indexinformation, or the like) when the transform and the quantization forthe residual block is not performed, that is, when the encoding for theresidual block is not performed and the prediction block generationinformation may be induced through the peripheral blocks of the currentblock. For example, when the prediction object block uses the intraprediction, the intra prediction mode information of the currentprediction object block may be induced based on the intra predictionmode information of the peripheral blocks to generate the predictionblock at the decoding end.

Another method may encode the prediction block generation information(for example, in the case of the intra prediction, the intra predictionmode information and in the case of the inter prediction, the motionvector, the reference picture index information, or the like) when thetransform and the quantization for the residual block is not performed,that is, when the encoding for the residual block is not performed andtransmit the encoded prediction block generation information to thedecoder.

In the case of the videos similar to the peripheral videos, the blocksimilar to the original block may be generated by only the predictionblock and therefore, the recovered prediction block may be used as therecovered video information without performing the transform, thequantization, and the entropy encoding on the residual block. Theinformation regarding whether the encoding is performed on the residualblocks may be represented as the intra skip flag that is the syntaxelement information.

The decoder may decode the information like the intra skip flag todetermine whether the entropy decoding is performed on the residualblocks.

FIG. 6 is a conceptual diagram illustrating a block decoding method inaccordance with an exemplary embodiment of the present invention.

Referring to FIG. 6 , the intra skip flag is decoded by the entropydecoder and it may be determined whether the residual blocks andprediction block generation information are decoded or the residualblocks and prediction block generation information are not decoded, onthe basis of the decoded intra skip flag. In addition, the intra skipflag is decoded by the entropy decoder and it may be determined whetherthe residual blocks are decoded or the residual blocks are not decoded,on the basis of the decoded intra skip flag.

(1) When the intra skip flag is 0, the prediction object block is ablock in which the residual blocks are also encoded and therefore, theentropy decoder decodes, dequantizes, and inversely transforms theresidual block information and then, adds the information to theprediction value of the prediction object block generated from thepredictor, thereby making it possible to recover the video.

(2) When the intra skip flag is 1, the prediction object block is ablock in which the residual blocks are not encoded and the recoveredvideo may be generated by only the prediction value of the predictionobject block generated from the predictor. In this case, in order togenerate the prediction value of the prediction object block, theprediction block generation information (for example, intra predictionmode information) is induced from the peripheral blocks without beingencoded or the prediction block generation information may be encoded soas to be transmitted to the decoding end. For example, the intraprediction mode information of the peripheral blocks is used as theintra prediction mode information of the prediction object block or theaverage value of the reference pixel may be used as the intra predictionvalue of the prediction object block.

In accordance with the exemplary embodiment of the present invention,the intra prediction method that may be used in the above-mentionedencoder and decoder is disclosed in FIGS. 5 and 6 .

Hereinafter, Table 1 and FIG. 7 illustrate the intra prediction modethat may be used in the exemplary embodiment of the present invention.However, Table 1 and FIG. 7 illustrate the intra prediction mode and theintra prediction mode used in the exemplary embodiment of the presentinvention is not limited to the intra prediction mode disclosed in FIG.7 .

Table 1 illustrates mapping between the intra prediction mode number andthe intra prediction mode.

TABLE 1 Intra prediction mode Associated names 0 Intra_Planar 1 Intra_DCOtherwise (2..34) Intra_Angular 35 Intra_FromLuma (used only for chroma)

Referring to Table 1, in order to perform the intra prediction on theprediction object block, the luminance block may use 35 intra predictionmodes of the screen. Among those, No. 2 intra prediction mode to No. 34intra prediction mode, which is the directional intra prediction mode,may perform the intra prediction based on the reference pixel indifferent directions. No. 0 and No. 1, which is the non-directionalintra prediction mode, generates the prediction pixel value of theprediction object block by using the reference pixel to perform theintra prediction. Here, the prediction mode number for the intra mode isan indicator, wherein each prediction mode is not limited to a specificnumber.

FIG. 7 is a conceptual diagram illustrating a directional intraprediction mode in accordance with an exemplary embodiment of thepresent invention.

Referring to FIG. 7 , the directional intra prediction mode may allocatethe intra prediction mode value from No. 34 intra prediction mode in aclockwise direction, starting from No. 2 intra prediction mode in thelower left direction.

FIG. 8 is a conceptual diagram illustrating an intra prediction methodin accordance with an exemplary embodiment of the present invention.

Referring to FIG. 8 , the intra prediction may be performed based on theperipheral reference pixel values of the prediction object block.

When the peripheral reference pixel values may be a 2 n upper referencepixel 800 from (x, y−1) to (x+2n−1, y−1) and a 2 n left reference pixel820 from (x−1, y) to (x−1, y+2n−1) when coordinates of the pixelpositioned at the upper left of the prediction object block having, forexample, an N×N size are set to be (x,y).

In accordance with the exemplary embodiment of the present invention,the intra prediction may be performed using the left reference pixelpresent at the left of the prediction object block and the upperreference pixel present at the upper of the prediction object block.

When the left reference pixel present at the left of the predictionobject block and the upper reference pixel present at the upper of theprediction object block are not available, the intra prediction may beperformed by padding the reference pixel. For example, like No. 34 intraprediction mode, the reference pixel for performing the intra predictionmay be pixels that are not currently decoded. As another example, whenthe prediction block is positioned at a boundary of an LCU, there may bethe case in which the pixel from n to upper 2 n−1 or the pixel from n toleft 2 n−1 are not available. In this case, the reference pixel forperforming the intra prediction is not present and therefore, thereference pixel value may be generated by padding the currentlyavailable pixel value into the non-available pixel value.

FIG. 9 is a conceptual diagram illustrating an intra prediction methodin accordance with an exemplary embodiment of the present invention.

Referring to FIG. 9 , the intra prediction may perform by only a part ofthe reference pixels and the information of the used reference pixel maybe encoded and transmitted to the decoding end. For example, theprediction value of the prediction object block is calculated by theaverage value of the reference pixel value but the reference pixel valuefor calculating the average value may be selectively used. When theintra prediction is performed using only the upper reference pixel, anaverage value of an upper reference pixel 900 may be used as theprediction value of the prediction object block and the information inwhich the upper reference pixel is used for the prediction by theencoder may be induced in the decoding end by using the correlation ofthe peripheral reference pixel values of the prediction object block. Inaddition, when the intra prediction is performed using only the upperreference pixel, the average value of the upper reference pixel 900 maybe used as the prediction value of the prediction object block and theinformation in which the upper reference pixel is used for theprediction by the encoder may be encoded and transmitted to the decodingend. In this case, the encoder may not transmit the prediction blockgeneration information (for example, the intra prediction modeinformation).

The reference pixel value illustrated in FIG. 9 is by way of example.Therefore, other reference pixel values (for example, the left referencepixel value or a part of the reference pixels) may be used for theprediction and various values such as an average value or anintermediate value obtained by allocating a weight value to thereference pixel rather than the average value of the pixels may be usedas the prediction value of the prediction object block.

FIG. 10 is a conceptual diagram illustrating an intra prediction methodin accordance with an exemplary embodiment of the present invention.

Referring to FIG. 10 , the reference pixel information may be used so asto perform the intra prediction on the prediction object block. Forexample, the reference pixel to be used for the intra prediction may bedetermined in the prediction object block by determining whether any oftwo values is larger by comparing the difference value between areference pixel 1020 positioned at the upper left of the predictionobject block and a left reference pixel 1040 and the difference valuebetween the reference pixel 1020 positioned at the upper left of theprediction object block and an upper reference pixel 1060.

The case in which the difference value between the reference pixel 1020positioned at the upper left of the prediction object block and the leftreference pixel 1040 is smaller than the difference value between thereference pixel 1020 positioned at the upper left of the predictionobject block and the upper reference pixel 1060 means that the pixelvalue is greater changed in the upper reference pixel direction than inthe left reference pixel direction and as a result, the intra predictionmay be performed by using the upper reference pixel for the intraprediction. On the other hand, the case in which the difference valuebetween the reference pixel 1020 positioned at the upper left of theprediction object block and the left reference pixel 1040 is larger thanthe difference value between the reference pixel 1020 positioned at theupper left of the prediction object block and the upper reference pixel1060 means that the pixel value of the left reference pixel direction isgreatly changed and as a result, the intra prediction may be performedby using the left reference pixel for the intra prediction.

Further, the opposite is also possible. For example, the case in whichthe difference value between the reference pixel 1020 positioned at theupper left of the prediction object block and the left reference pixel1040 is smaller than the difference value between the reference pixel1020 positioned at the upper left of the prediction object block and theupper reference pixel 1060 means that the pixel value is greater changedin the upper reference pixel direction than in the left reference pixeldirection and as a result, the intra prediction may be performed byusing the left reference pixel for the intra prediction.

When the difference value between the reference pixel 1020 positioned atthe upper left of the prediction object block and the left referencepixel 1040 and the difference value between the reference pixel 1020positioned at the upper left of the prediction object block and theupper reference pixel 1060 have little difference from each other, theintra prediction may be performed by using a planar mode or a DC modethat is an non-directional prediction mode.

In accordance with another exemplary embodiment of the presentinvention, the value arithmetically calculated by mixing severalprediction methods may be used the intra prediction value of the block,upon performing the intra prediction by using the intra prediction.

For example, the intra prediction may be performed by using the averagevalue or of values calculated by using the intra prediction valuepredicted by the plurality of intra prediction modes or a sum of weightvalues.

FIG. 11 is a conceptual diagram illustrating a method for determiningwhether residual blocks are generated in accordance with an exemplaryembodiment of the present invention.

In accordance with the exemplary embodiment of the present invention,the block may be recovered only by the prediction blocks withoutgenerating the residual blocks according to the video. In this case,whether the recovered block is a block recovered by only the predictionblock or a block generating the original block based on the predictionblock by the residual block value should be determined. In this case, soas to encode whether the prediction object block is a block generatingthe residual blocks or is a block configured of only the predictionblock, the encoding related information of the peripheral blocks may beused.

Referring to FIG. 11 , a single LCU may be divided into a plurality ofCUs, wherein the single CU may be divided into a plurality of PUs. Thesingle prediction blocks may perform the intra prediction or the interprediction and the residual block that is the difference value with theoriginal block may be generated based on the prediction block calculatedby the prediction method. In accordance with the exemplary embodiment ofthe present invention, the plurality of PUs included in the single LCUmay be configured of only the prediction block and the information inwhich the prediction block generation information is not separatelytransmitted may be transmitted to the decoder, only the prediction blockinformation may be encoded and transmitted to the decoder, or both ofthe prediction block generation information and the residual blockinformation may be encoded and transmitted to the decoder. Theinformation related to whether the residual block for each predictionblock is transmitted may be decoded based on the predetermined syntaxelement. When the information related to whether the residual blockinformation is transmitted is encoded, the information related towhether the residual blocks of the peripheral blocks are transmitted issubjected to the entropy encoding, the video information may betransmitted by using a small number of bits while reflecting thetendency of the video.

For example, each PU may transmit the information related to whether theresidual block is transmitted as the predetermined flag information.Upon decoding the flag information, the entropy decoding may beperformed based on whether the residual blocks of the peripheral blocksare transmitted by using the entropy encoding method such as CABAC,CAVLC. The information regarding whether the residual block of the blockis transmitted may be transmitted while reflecting the predeterminedtendency present in the video by encoding the prediction object blockbased on the video information on the plurality of blocks of theperipheral blocks.

The following Table 2 shows a syntax structure representing a method fortransmitting the information regarding whether the residual block of theblock is transmitted. In the following syntax, mb represents a specificblock unit and is not limited to a macro block and therefore, may be aprediction unit such as the PU and may be various block units accordingto the implementation. Further, the syntax element to be described belowmay be represented in various syntax element types having the same orsimilar meaning and the syntax element information performing thefollowing role or the syntax element information for implementing theprinciple of the present invention is included in the scope of thepresent invention.

TABLE 2 slice_data( ) { C Descriptor

 else if( slice_type == I || slice_type == SI )  {   if(!entropy_coding_mode_flag ) {    mb_intra_skip_run 2 ue(v)   prevMbSkipped = (mb_skip_run > 0 )    for( i=0; i<mb_skip_run; i++ )    CurrMbAddr = NextMbAddress( CurrMbAddr )    moreDataFlag =more_rbsp_data ( )   } else {    mb_intra_skip_flag 2 ae(v)   moreDataFlag = !mb_intra_skip_flag   }  }

  if( slice_type == I || slice_type == SI )    prevMbSkipped =mb_intra_skip_flag

Referring to Table 2, the block information may be decoded bydifferentiating the slice type information so as to encode whether theblock included in the corresponding video unit includes the residualblock information in the predetermined upper level syntax structure likethe slice level.

For example, when the slice type is not configured of only the intraprediction block (ii), it may be represented whether the block is ablock encoded including the residual block information by using thesyntax element mb_skip_run and mb_skip_flag according to the entropyencoding method entropy_coding_mode_flag. The intra skip flag may bedefined as the term including the syntax element mb_skip_run and themb_skip_flag.

The mb_skip_run is a flag used when using the CAVLC as the entropyencoding method. For example, when the mb-skip_run value is 1, it is ablock configured of only the prediction block information withouttransmitting the residual block information and when the mb_skip_runvalue is 0, it may be used as a meaning called a block transmitting theresidual block information. The mb_skip_flag is a flag used when usingthe CABAC as the entropy encoding method. For example, when themb-skip_flag value is 1, it is a block configured of only the predictionblock information without transmitting the residual block informationand when the mb_skip_flag value is 0, it may be used as a meaning calleda block transmitting the residual block information.

Even when the slice type is not configured of only the intra predictionblock as the I slice, it may be represented whether the block is a blockencoded including the residual block information by using the syntaxelement mb_intra_skip_run and mb_intra_skip_flag according to theentropy encoding method entropy_coding_mode_flag.

The mb_intra_skip_run is a flag used when using the CAVLC as the entropyencoding method. For example, when the mb_intra_skip_run value is 1, itis a block configured of only the prediction block information withouttransmitting the residual block information and when themb_intra_skip_run value is 0, it may be used as a meaning called a blocktransmitting the residual block information. The mb_intra_skip_flag is aflag used when using the CABAC as the entropy encoding method. Forexample, when the mb_intra_skip_flag value is 1, it is a blockconfigured of only the prediction block information without transmittingthe residual block information and when the mb_intra_skip_flag value is0, it may be used as a meaning called a block transmitting the residualblock information.

Whether the previously encoded or decoded block is encoded including theresidual block information is stored as prevMbskipped and may be usedwhen performing the entropy encoding on the mb_intra_skip_run or themb_intra_skip_flag that is the flag information of the next block.

The following Table 3 shows another syntax structure representing amethod for transmitting the information regarding whether the residualblock of the block is transmitted.

TABLE 3 macroblock_layer( ) { C Descriptor  if ( ! mb_skip_flag )  intra_skip_flag 2 u(1) | ae(v)  if ( !intra skip flag ) {

Referring to Table 3, when the mb_skip_flag or the mb_intra_skip_flag is1, the residual block information is absent and therefore, the residualblock information is not decoded and when the mb_skip_flag or themb_intra_skip_flag is 0, the residual block information is present andtherefore, the residual block may be decoded by the process of decodingthe residual block information.

FIG. 12 is a flow chart illustrating a video decoding method inaccordance with an exemplary embodiment of the present invention.

Referring to FIG. 12 , it is determined whether the residual blockinformation of the prediction object block is present (S1200).

In accordance with the exemplary embodiment of the present invention,the prediction object block may be divided into the block in which theresidual block information is encoded together with the prediction blockor the block in which only the prediction block is encoded, wherein theinformation may be subjected to the entropy decoding as the flaginformation.

The prediction object block may be divided into the block in which theresidual block information is encoded together with the prediction blockor the block in which only the prediction block is encoded, based on theentropy decoded information and may determine whether the residual blockinformation is additionally decoded.

When the residual block information is present, the prediction objectblock is recovered based on the prediction block information and theresidual block information (S1210).

When the residual block information is absent, the prediction blockgeneration information is induced through the peripheral blocks of theprediction object block to recover the prediction object block (S1220).

Only the information in which the prediction object block is configured(generated) of only the prediction value is recovered based on thedecoded information to generate the prediction block. As describedabove, when the method for generating the prediction block using theperipheral reference pixel information of the prediction object block isused, the decoder does not need to separately decode the information forgenerating the prediction block. In accordance with another exemplaryembodiment of the present invention, it is possible to recover theprediction object block by decoding a value encoding the predictionblock generation information such as the intra prediction modeinformation by the encoder.

FIG. 13 is a conceptual diagram illustrating a method for recovering amulti-dimensional video in accordance with an exemplary embodiment ofthe present invention.

Referring to FIG. 13 , the depth map information is recovered so as torecover the multi-dimensional video (S1300).

The multi-dimensional video may be configured of a plurality of videossuch as the depth map information and the pixel sample value information(luminance information video, color difference information video) Thefollowing exemplary embodiment describes the method that does nottransmit the residual block information to only the depth map videobased on the video information but the above-mentioned method may alsobe used for the pixel sample information and the exemplary embodiment isalso included in the scope of the present invention.

The depth map information is the information related to the depthinformation of video and may be the video having the high correlation inthe vertical or horizontal direction according to the video. Asdescribed above, in order to recover the depth map information, theprediction object block may be divided into the block in which theresidual block information is encoded together with the prediction blockor the block in which only the prediction block is encoded, based on theentropy decoded information and may determine whether the residual blockinformation is additionally decoded. The information for generating theprediction block is encoded or transmitted or may be used by beinginduced from the peripheral recovered blocks.

A pixel information frame is recovered (S310).

The pixel information frame such as a luminance information frame, acolor difference frame, or the like, may be recovered according to theconfiguration of the video.

A three-dimensional video frame is output based on the decoded depth mapinformation frame and the pixel information frame (S1320).

The decoder may recover the three-dimensional video frame based on thedecoded depth map information frame and the pixel information frame.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims. Accordingly, suchmodifications, additions and substitutions should also be understood tofall within the scope of the present invention.

1. An image decoding method, comprising: extracting encoding informationindicating whether residual block information for a target block ispresent in a bitstream from the bitstream; and generating areconstruction block for the target block based on the encodinginformation, wherein: the reconstruction block is generated based on aprediction block for the target block, and the generating of thereconstruction block comprises: generating the reconstruction blockbased on intra prediction which uses an intra prediction direction forthe target block in a case that the encoding information indicates thatthe residual block information is not present, wherein: the intraprediction direction determines one or more reference pixels used forthe intra prediction, and values for the encoding information toindicate whether the residual block information is present are 0 and 1.2. The image decoding method of claim 1, wherein: the generating thereconstruction block comprises: generating the reconstruction blockbased on an intra prediction value of the target block and the residualblock information in a case that the encoding information indicates thatthe residual block information is present.
 3. The image decoding methodof claim 2, wherein: the reconstruction block is generated using only anintra prediction value generated based on the intra prediction directionfor the target block in a case that the encoding information indicatesthat the residual block information is not present.
 4. The imagedecoding method of claim 2, wherein: the intra prediction value is avalue calculated based on pixel values of reference pixels for thetarget block, and the intra prediction value is a value predicted valueusing a directionality according to a specific intra prediction value,or an arithmetic average or weighted average of the pixel values of thereference pixels.
 5. An image decoding method, comprising: extractingencoding information indicating whether residual block information for atarget block is present in a bitstream from the bitstream; andgenerating a reconstruction block for the target block based on theencoding information, wherein: the reconstruction block is generatedbased on a prediction block for the target block, the reconstructionblock is generated based on intra prediction which uses an intraprediction direction for the target block in a case that the encodinginformation indicates that the residual block information is notpresent, the intra prediction direction determines one or more referencepixels used for the intra prediction, and values for the encodinginformation to indicate whether the residual block information ispresent are 0 and
 1. 6. An image encoding method, comprising: generatingencoding information indicating whether residual block information isused in generating a reconstruction block for a target block; andgenerating the reconstruction block for the target block, wherein: indecoding for the target block, the reconstruction block is generatedbased on a prediction block for the target block, in decoding for thetarget block, the reconstruction block is generated based on intraprediction using an intra prediction direction for the target block in acase that the encoding information indicates that the residual blockinformation is not used, the intra prediction direction determines oneor more reference pixels used for the intra prediction, and values forthe encoding information to indicate whether the residual blockinformation is present are 0 and
 1. 7. The image encoding method ofclaim 6 wherein: in decoding for the target block, the reconstructionblock is generated using an intra prediction value of the target blockand the residual block information in a case that the encodinginformation indicates that the residual block information is used. 8.The image encoding method of claim 7 wherein” in decoding for the targetblock, the reconstruction block is generated using only an intraprediction value generated based on the intra prediction direction forthe target block in a case that the encoding information indicates thatthe residual block information is not used.
 9. The image decoding methodof claim 7 wherein: the intra prediction value is a value calculatedbased on pixel values of reference pixels for the target block, and theintra prediction value is a value predicted value using a directionalityaccording to a specific intra prediction value, or an arithmetic averageor weighted average of the pixel values of the reference pixels.
 10. Anon-transitory computer-readable recording medium storing a bitstreamgenerated by the image encoding method of claim
 6. 11. An image encodingmethod, comprising: generating encoding information for a target block;and generating a bitstream comprising the encoding information, wherein:the encoding information indicates whether residual block informationfor generating a reconstruction block for the target block is present inthe bitstream, in decoding for the target block, the reconstructionblock is generated based on a prediction block for the target block, indecoding the target block, the reconstruction block is generated basedon intra prediction which uses an intra prediction direction for thetarget block in a case that the encoding information indicates that theresidual block information is not present, the intra predictiondirection determines one or more reference pixels used for the intraprediction, and values for the encoding information to indicate whetherthe residual block information is present are 0 and
 1. 12. The imageencoding method of claim 11, wherein: in decoding for the target block,the reconstruction block is generated using an intra prediction value ofthe target block and the residual block information in a case that theencoding information indicates that the residual block information ispresent.
 13. The image encoding method of claim 12, wherein: in decodingfor the target block, the reconstruction block is generated using onlyan intra prediction value generated based on the intra predictiondirection for the target block in a case that the encoding informationindicates that the residual block information is not present.
 14. Theimage decoding method of claim 9, wherein: in decoding for the targetblock, the intra prediction value is a value calculated based on pixelvalues of reference pixels for the target block, and in decoding for thetarget block, the intra prediction value is a value predicted valueusing a directionality according to a specific intra prediction value,or an arithmetic average or weighted average of the pixel values of thereference pixels.
 15. A non-transitory computer-readable recordingmedium storing a bitstream generated by the image encoding method ofclaim
 11. 16. A non-transitory computer-readable recording mediumstoring a bitstream for decoding an image, the bitstream comprising:encoding information indicating whether residual block information for atarget block is present in the bitstream, wherein: a reconstructionblock for the target block is generated based on the encodinginformation, the reconstruction block is generated based on a predictionblock for the target block, the reconstruction block is generated basedon intra prediction which uses an intra prediction direction for thetarget block in a case that the encoding information indicates that theresidual block information is not present, the intra predictiondirection determines one or more reference pixels used for the intraprediction, and values for the encoding information to indicate whetherthe residual block information is present are 0 and
 1. 17. Thenon-transitory computer-readable recording medium of claim 16, whereinthe reconstruction block is generated based on an intra prediction valueof the target block and the residual block information in a case thatthe encoding information indicates that the residual block informationis present.
 18. The non-transitory computer-readable recording medium ofclaim 17, wherein the reconstruction block is generated using only anintra prediction value generated based on the intra prediction directionfor the target block in a case that the encoding information indicatesthat the residual block information is not present.
 19. Thenon-transitory computer-readable recording medium of claim 17, wherein:the intra prediction value is a value calculated based on pixel valuesof reference pixels for the target block, and the intra prediction valueis a value predicted value using a directionality according to aspecific intra prediction value, or an arithmetic average or weightedaverage of the pixel values of the reference pixels.